Problems: 1) the brain size threshold appears to be crossed later when it exceeds 1000 cc with H. erectus; 2) language cannot be inferred from brain casts; 3) chimps and Australopithecines had opposable thumbs (and if chimps can make tools, A. could also probably make tools); 4) stone tools date to a period when either Australopithecines or Homo could have been the first tool makers.

Bipedalism

6-4.5 MYA

Butchering-

2.5 MYA

Stone Tool Technology:

Pre-Oldowan
Oldowan
Acheulean
Mousterian
Upper Paleolithic

(Stone Tool Technology:)
Pre-Oldowan-

3.1-2.6 MYA, Australopithecus?/ Early Homo

(Stone Tool Technology:)
Oldowan-

2.6-1.5 MYA, Australopithecus?/ Early Homo

(Stone Tool Technology:)
Acheulean-

1.5 MYA- 200 KYA,
H. erectus

(Stone Tool Technology:)
Mousterian-

200-40 KYA,
H. Neanderthalensis/ H. Sapiens

(Stone Tool Technology:)
Upper Paleolithic-

90/40-12 KYA,
H. Neanderthalensis/ H. sapiens

Larynx-

Voice box

High larynx-

Most mammals have this. It limits sound production.

Low larynx-

Humans have this. Allows for the production of a greater range of sounds (acts sort of like an "echo chamber")

Some analyzation of the skull-

Australopithecines had flat skull bases (4-1 MYA), H. erectus had a slightly curved skull base (1.5 MYA), and that modern curvature to the skull base was reached only about 300 KYA (suggesting that prior to 300 KYA, hominids had a limited range of sound production).